The present invention relates to the reaction of hydrogen gas with vanadium-based metal alloys and more particularly to the rapid reaction at mild temperatures of hydrogen gas with solid solution alloys having a body-centered cubic structure and having a formula V.sub.1-x M.sub.x, wherein M is manganese, chromium, cobalt, iron, nickel or mixtures thereof and wherein x varies from at least about 2 atom percent up to the solubility limit of cobalt, iron or nickel and up to about 20 mol percent of manganese and up to about 40 mol percent of chromium in said solid solution alloys.
Most metals that form hydrides react very slowly in bulk for at room temperature with hydrogen gas. Metallic niobium and metallic vanadium, for example, are relatively inert in bulk form at room temperature in the presence of hydrogen gas, with the hydrogen only slowly reacting with the body-centered cubic structure of each metal to form a precipitated niobium hydride or vanadium hydride. Most other metals that form hydrides react in a similar fashion, with the rate of solution in the alpha phase formation and hydride formation varying among metals and alloys, but rarely occurring at room temperature in less than one hour. In the case of niobium, attempts to increase this rate by plating over niobium with nickel or palladium or iron have been reported.
In our co-pending, U.S. application Ser. No. 365,119, filed Apr. 5, 1982, it is disclosed that solid solution alloys of niobium or tantalum and a second metal such as aluminum, cobalt, manganese, molybdenum or vanadium react rapidly with hydrogen under mild conditions.
Metallic titanium is also relatively inert in the bulk form at room temperature in the presence of hydrogen gas, with hydrogen reacting only slowly with the hexagonal close packed structure of the metal to form a precipitated titanium hydride.
In our co-pending U.S. patent application Ser. No. 420,405 filed on Sept. 20, 1982, it is disclosed that various titanium-based solid solution alloys rapidly react with hydrogen at room temperature to form the corresponding hydrides. The titanium-based solid solution alloys have a body-centered cubic structure that comprises titanium and a second metal such as molybdenum, vanadium or niobium; when said second metal in said binary alloy is vanadium or niobium and, optionally, when said second metal is molybdenum, at least about 1 atom percent of a third metal such as aluminum, cobalt or iron is dissolved in said binary alloy.
For many applications of metal hydrides, such as hydrogen recovery, it is desirable to form the hydride from bulk metal, pulverize the hydride into some form of granular or powder structure, and thereafter cyclically remove hydrogen to form a lower hydride or the hydrogen-free metal and thereafter reintroduce hydrogen to reform the hydride. Starting with bulk metal or bulk alloy, it is normally necessary to go through an induction period, wherein the metal is heated to a temperature such as 300.degree.-700.degree. C., then reacted with hydrogen at high pressure and then cooled very slowly until a temperature below about 100.degree. C., and preferably about room temperature, is reached. At the higher temperature, the rate of hydrogen dissolving in the metal (the alpha phase) is increased so as to achieve saturation in a matter of minutes rather than hours or days. At the high temperature, however, the equilibrium hydrogen pressure is so high that relatively little hydrogen actually dissolves or forms hydride. Accordingly, it is only upon gradual cooling that hydrides form. See, for example, U.S. Pat. No. 4,075,312 (Tanaka et al.) which discloses titanium alloy hydride compositions containing at least one metal selected from the group consisting of vanadium, chromium, manganese, molybdenum, iron, cobalt, and nickel.
U.S. Pat. No. 4,318,897 (Gonczy) discloses ferrovanadium alloys containing from about 5 to about 30% by weight iron, which may be used for hydrogen storage systems. However, U.S. Pat. No. 4,318,897 also discloses it is necessary to preactivate the ferrovanadium alloys by heating same in a vacuum at 400.degree.-650.degree. C. and thereafter exposing the alloy to hydrogen.
Kirschfeld et al. in "Zeitschrift for Elektrochemie,". Vol. 36, 1930, pp. 123-129 discloses that ferrovanadium alloys containing 29-90 by weight iron are heated to high temperatures in the presence of hydrogen to form the corresponding metal hydrides.
Thus, with the exception of the ongoing research in our laboratories, in all these disclosures, an initial induction period at a high temperature in the presence of hydrogen is required for hydride formation.
While many metals require only a single induction process to form the hydride, with the subsequent hydride powder cycling at a reasonable reaction rate, it should be apparent that the induction process represents a distinct disadvantage in forming and utilizing metal hydrides.